Study: Americans may be exposed to potential carcinogens while driving
As Americans head toward a hot summer packed with car travels, drivers might want to be mindful of potential harmful chemicals inside their vehicles.
According to a study published this week in the journal Environmental Science & Technology, flame retardants — chemicals typically added to seat foam and other automobile materials to prevent fires — are present within almost all brands of cars, at least among models dating from 2015. When seasonal temperatures spike, so too do the concentrations of flame retardants circulating inside a car’s cabin: as much as two to five times more in summer compared with winter, researchers from Duke University and the California-based environmental advocacy group the Green Science Policy Institute found.
Arlene Blum, executive director of the institute who co-authored the study, told The Dallas Morning News that flame retardant chemicals have been incorporated into consumer goods, such as clothing and furniture, since the 1970s. “Flame retardants were put into a variety of products with the idea that they would improve fire safety,” Blum said. “Nobody thought they were harmful.”
Later studies uncovered evidence suggesting flame retardants may pose a serious health risk. For example, a 2010 study by the University of California, Berkeley, and the Centers for Disease Control and Prevention found a type of flame retardant called polybrominated diphenyl ethers (or PBDES) was associated with disrupting normal thyroid function during pregnancy. Other studies have found associations with one’s cancer risk and neurodevelopmental disorders.
In the new paper, Blum and her colleagues found that among 101 cars — spread out across 30 states — the major flame retardant chemicals present were organophosphate esters (OPES). These chemicals are also mixed into materials to make them more pliable and plastic.
Participants hung silicone wristbands from their rearview mirrors for a week both during the winter and summer. Blum said the silicone passively absorbs any chemicals free-floating in the cabin air. Some 51 participants also collected and sent the researchers little nuggets of car seat foam.
Half of cars tested were gasoline-powered, a quarter were all electric, and the remaining quarter were hybrids.
While individual car cabin temperature wasn’t directly measured, the researchers used data from the National Oceanic and Atmospheric Administration’s online Climate Database to associate the concentration of flame retardants with ambient temperature wherever the vehicle was geographically located.
OPES were the most abundant out of all 49 flame retardants detected. One particular OPE, called tris (1-chloro-isopropyl) phosphate (or TCIPP, for short), had an outsized presence compared with any other flame retardant. It was also the primary one found in car seat foam.
The overall ambient temperatures ran anywhere from around 23 degrees Fahrenheit to 86 degrees Fahrenheit. When summertime rolled around, Blum and her colleagues saw levels for multiple OPES, including TCIPP, bump up in cars. This likely happens because OPES are physically rather than chemically mixed into materials, so they tend to leach out into their immediate environment, especially when prompted by warmer temperatures.
Dohyeong Kim, director of the Geospatial Health Research Group at the University of Texas at Dallas, who was not involved in the study, said the new research was the very first to “really look into potential concerns on flame retardants in cars, but we need more evidence to really take action.”
Kim said the more evidence required is how flame retardant exposure while driving correlates with health outcomes. Kristina Whitworth, an associate professor at Baylor College of Medicine’s Center for Precision Environmental Health, agreed. She was not involved in the new study.
“[This study] is not assessing human exposure,” Whitworth said. “There would really have to be other studies done to understand whether this kind of exposure to the levels in a vehicle adversely impacts health… We would also have to be able to place these measured levels in the context of other studies that have demonstrated, for example, toxicity.”
Whitworth added that while some OPES, like TCIPP, are being investigated as potential carcinogens, scientists would need to figure out at what concentration of human exposure these chemicals are cancer-causing.
For example, in 2023, it took the average North Texan traveling through Dallas-fort Worth city centers around 11 minutes and 15 seconds to drive 6 miles, according to digital mapping company Tomtom. Whether this duration — or anything more or less — is considered enough exposure to be considered harmful is hard to say.
If you’re wondering whether opening windows or running the air conditioning can mitigate flame retardant exposure, that also remains to be seen, said Elaine Symanski, also a professor at Baylor College of Medicine’s Center for Precision Environmental Health, who was not involved in the study.
“Does opening windows reduce exposure? It does, but to what extent?” Symanski said. “What about air conditioning? These could be important determinants of cabin level or exposure that, in this instance, we don’t know.”
But Blum hopes this study and others that follow will spearhead federal policy change. Flame retardants like TCIPP are added to car seat foam to meet the U.S. National Highway Traffic Safety Administration’s (NHTSA) Federal Motor Vehicle Safety Standard 302, which was adopted in 1971 and remains unchanged. In light of the new research, a Consumer Reports petition is urging NHTSA to revise its flammability standards for the interior materials of cars.
In an email to The Dallas Morning News, NHTSA’S director of media relations Lucia Sanchez wrote that the agency was “aware of this [study] and is reviewing it.”